From Unknown Idol to Popular Idol

After a traffic accident, he comes to his senses and finds that three years have passed. He was an unknown idol, but now he’s become a top popular idol, and the members who used to make him uncomfortable are acting friendly toward him. He lost the memories of those three years? During the three years he has no memory of, did he really bring the group to where it is now?

Songs he never sang, words and actions he never did. In the broadcast records from that time, he is acting like an entirely different person from his true self. And then he finds a diary written by someone else. It says someone had "possessed" his body.

The person everyone knows is not actually him. If everyone wants him to return to that time when someone else had possessed him, then who exactly is he?